1. Field of the Invention
The present invention relates generally to a lumbar support regulating apparatus in a seat back and more particularly to such an apparatus in a vehicle seat back.
2. Description of the Prior Art
In general, the use of a lumbar support regulating apparatus in the seat back of a motor vehicle seat is known so that the hardness of the cushion of the seat back which is in contact with the lumbar region of a person seated on the seat can be suitably regulated. Conventionally, a cam mechanism or a combination wire and link mechanism are in wide use for regulating the hardness of the cushion of the seat back. However, the cam mechanisms currently in use can only perform a stepped regulation and it is impossible to obtain fine adjustments. The combination wire and link mechanisms have poor lasting qualities since the wire is always maintained in a strained condition. Furthermore, such a wire and link mechanism makes it difficult to enlarge the regulating stroke in a limited space and the arrangement is unstable upon vibration or impact.